JP5035313B2 - Negative electrode for lithium ion secondary battery and method for producing the same - Google Patents
Negative electrode for lithium ion secondary battery and method for producing the same Download PDFInfo
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- JP5035313B2 JP5035313B2 JP2009220519A JP2009220519A JP5035313B2 JP 5035313 B2 JP5035313 B2 JP 5035313B2 JP 2009220519 A JP2009220519 A JP 2009220519A JP 2009220519 A JP2009220519 A JP 2009220519A JP 5035313 B2 JP5035313 B2 JP 5035313B2
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- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims description 25
- 229910001416 lithium ion Inorganic materials 0.000 title claims description 25
- 238000004519 manufacturing process Methods 0.000 title claims description 11
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- 125000003545 alkoxy group Chemical group 0.000 claims description 25
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- 229910052718 tin Inorganic materials 0.000 description 12
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- 239000007773 negative electrode material Substances 0.000 description 9
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 8
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- 238000011156 evaluation Methods 0.000 description 8
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- 125000002496 methyl group Chemical group [H]C([H])([H])* 0.000 description 5
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- 125000000913 palmityl group Chemical group [H]C([*])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])[H] 0.000 description 2
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- 125000003944 tolyl group Chemical group 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- LCZUOKDVTBMCMX-UHFFFAOYSA-N 2,5-Dimethylpyrazine Chemical compound CC1=CN=C(C)C=N1 LCZUOKDVTBMCMX-UHFFFAOYSA-N 0.000 description 1
- 239000004593 Epoxy Substances 0.000 description 1
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- CKFRRHLHAJZIIN-UHFFFAOYSA-N cobalt lithium Chemical compound [Li].[Co] CKFRRHLHAJZIIN-UHFFFAOYSA-N 0.000 description 1
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Classifications
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/139—Processes of manufacture
- H01M4/1395—Processes of manufacture of electrodes based on metals, Si or alloys
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
- H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/134—Electrodes based on metals, Si or alloys
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/621—Binders
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
- H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
- H01G11/22—Electrodes
- H01G11/26—Electrodes characterised by their structure, e.g. multi-layered, porosity or surface features
- H01G11/28—Electrodes characterised by their structure, e.g. multi-layered, porosity or surface features arranged or disposed on a current collector; Layers or phases between electrodes and current collectors, e.g. adhesives
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Description
本発明は、リチウムイオン二次電池用負極及びその製造方法に関するものである。 The present invention relates to a negative electrode for a lithium ion secondary battery and a method for producing the same.
電子機器の小型化、軽量化が進み、その電源としてエネルギー密度の高い二次電池が望まれている。二次電池とは、電解質を介した化学反応により正極活物質と負極活物質が持つ化学エネルギーを外部に電気エネルギーとして取り出すものである。このような二次電池において、実用化されているなかで高いエネルギー密度を持つ二次電池はリチウムイオン二次電池である。 As electronic devices become smaller and lighter, secondary batteries with high energy density are desired as power sources. A secondary battery is one that extracts chemical energy of a positive electrode active material and a negative electrode active material as electric energy to the outside by a chemical reaction via an electrolyte. Among such secondary batteries, a secondary battery having a high energy density among the practically used secondary batteries is a lithium ion secondary battery.
リチウムイオン二次電池には、正極の活物質として主にリチウムコバルト複合酸化物等のリチウム含有金属複合酸化物が用いられ、負極の活物質としてはリチウムイオンの層間への挿入(リチウム層間化合物の形成)及び層間からのリチウムイオンの放出が可能な多層構造を有する炭素材料が主に用いられている。 In lithium ion secondary batteries, lithium-containing metal composite oxides such as lithium cobalt composite oxide are mainly used as the positive electrode active material, and lithium ion insertion (interlayer of lithium intercalation compounds) is used as the negative electrode active material. And carbon materials having a multilayer structure capable of releasing lithium ions from the interlayer are mainly used.
正、負極の極板は、これらの活物質とバインダー樹脂と導電材とを溶剤に分散させてスラリーとしたものを集電体である金属箔上に両面塗布し、溶剤を乾燥除去して合剤層を形成後、これをロールプレス機で圧縮成形して作製されている。 The positive and negative electrode plates are prepared by dispersing these active materials, binder resin and conductive material in a solvent to form a slurry on both sides of a metal foil as a current collector, and removing the solvent by drying. After forming the agent layer, it is produced by compression molding with a roll press.
また、近年リチウムイオン二次電池の負極活物質として炭素材料の理論容量を大きく超える充放電容量を持つ次世代の負極活物質の開発が進められている。例えばSiやSnなどリチウムと合金化可能な金属を含む材料が期待されている。 In recent years, a next-generation negative electrode active material having a charge / discharge capacity that greatly exceeds the theoretical capacity of a carbon material has been developed as a negative electrode active material of a lithium ion secondary battery. For example, a material containing a metal that can be alloyed with lithium such as Si or Sn is expected.
SiやSnなどを活物質に用いる場合、これらの材料は、充放電時のLiの吸蔵・放出に伴う体積変化が大きいため、集電体との接着状態を良好に維持することが難しい。また、これらの材料はリチウムの挿入、脱離に伴う体積変化率が非常に大きく、充放電サイクルによって膨張、収縮を繰り返し、活物質粒子が微粉化したり、脱離したりするため、サイクル劣化が非常に大きいという欠点がある。 When Si, Sn, or the like is used as an active material, these materials have a large volume change associated with insertion and extraction of Li during charge and discharge, and it is difficult to maintain a good adhesion state with the current collector. In addition, these materials have a very large volume change rate due to the insertion and desorption of lithium, and are repeatedly expanded and contracted by the charge / discharge cycle, so that the active material particles are pulverized or desorbed. Has the disadvantage of being large.
サイクル特性を向上させるため、活物質が剥離、脱落しにくくするために様々なバインダー樹脂や活物質の組み合わせが検討されている。 In order to improve the cycle characteristics, various combinations of binder resins and active materials have been studied in order to make it difficult for the active material to peel and drop off.
特許文献1では、バインダー樹脂としてアルコキシル基含有樹脂を用いる二次電池用電極が提案されている。 Patent Document 1 proposes an electrode for a secondary battery using an alkoxyl group-containing resin as a binder resin.
特許文献1に記載のように活物質と、それを結着させるバインダー樹脂との組み合わせについて各種検討されているが、サイクル性能向上の余地があり、よりサイクル性能の優れた次世代の活物質を用いたリチウムイオン二次電池用負極が求められている。 Various studies have been made on the combination of an active material and a binder resin that binds the active material as described in Patent Document 1. However, there is room for improvement in cycle performance, and a next-generation active material with better cycle performance has been developed. There is a demand for a negative electrode for a lithium ion secondary battery used.
本発明は、このような事情に鑑みて為されたものであり、リチウムの吸蔵・放出に伴う体積変化が大きい活物質の集電体からの剥離、脱落をさらに抑制することで優れたサイクル性能を有するリチウムイオン二次電池用負極及びその製造方法を提供することを目的とする。 The present invention has been made in view of such circumstances, and has excellent cycle performance by further suppressing the separation and dropping of the active material from the current collector, which has a large volume change associated with insertion and extraction of lithium. It aims at providing the negative electrode for lithium ion secondary batteries which has, and its manufacturing method.
本発明者等が鋭意検討した結果、活物質層が球状シリコーンゴム粉体にシリコーンレジンを被覆したシリコーン複合粉体からなる緩衝材を含むと優れたサイクル性能を有するリチウムイオン二次電池用負極を提供することが出来ることを見いだした。 As a result of intensive studies by the present inventors, a negative electrode for a lithium ion secondary battery having an excellent cycle performance when the active material layer includes a buffer material made of a silicone composite powder in which a silicone resin is coated on a spherical silicone rubber powder. I found what I could offer.
すなわち、本発明のリチウムイオン二次電池用負極は、集電体と前記集電体の表面に固定させた活物質層とを有するリチウムイオン二次電池用負極において、活物質層は、活物質、バインダー、導電材、及び緩衝材を含み、活物質はSiおよび/またはSnを含み、
緩衝材は球状シリコーンゴム粉体にシリコーンレジンを被覆したシリコーン複合粉体からなることを特徴とする。
That is, the negative electrode for a lithium ion secondary battery of the present invention is a negative electrode for a lithium ion secondary battery having a current collector and an active material layer fixed on the surface of the current collector. A binder, a conductive material, and a buffer material, and the active material contains Si and / or Sn,
The buffer material is characterized by comprising a silicone composite powder obtained by coating a silicone resin on a spherical silicone rubber powder.
上記シリコーン複合粉体は衝撃吸収性に優れている。そのため、上記活物質層に上記シリコーン複合粉体を緩衝材として含むことにより、充放電時のLiの吸蔵・放出に伴う体積変化を吸収して活物質の剥離、脱落を抑制していると考えられる。 The silicone composite powder is excellent in impact absorption. Therefore, by including the silicone composite powder as a buffer material in the active material layer, it is considered that the volume change associated with insertion / extraction of Li during charge / discharge is absorbed to suppress separation and dropping of the active material. It is done.
バインダーはポリイミド樹脂硬化物あるいはアルコキシル基含有シラン変性ポリイミド樹脂硬化物を含むことが好ましい。バインダーがポリイミド骨格を持つため、バインダーの強度が強く、耐熱性及び耐久性に優れる。 The binder preferably includes a cured polyimide resin or a cured silane-modified polyimide resin containing an alkoxyl group. Since the binder has a polyimide skeleton, the strength of the binder is strong, and the heat resistance and durability are excellent.
アルコキシル基含有シラン変性ポリイミド樹脂硬化物は、樹脂とシリカのハイブリッド体であり、無機成分である集電体や活物質、導電材及び緩衝材とも密着性がよく、集電体に活物質等を強固に保持できる。 The alkoxyl group-containing silane-modified polyimide resin cured product is a hybrid of resin and silica, and has good adhesion to current collectors and active materials, conductive materials and buffer materials, which are inorganic components. Can hold firmly.
活物質層の総量を100質量%としたときに、上記緩衝材は1質量%〜20質量%含有されることが好ましい。 When the total amount of the active material layer is 100% by mass, the buffer material is preferably contained in an amount of 1% by mass to 20% by mass.
上記緩衝材を1質量%〜20質量%含有することにより、高容量かつサイクル特性に優れる負極とすることが出来る。緩衝材が20質量%より多く含有されると、活物質の含有量が減り、電池容量が少なくなる。また緩衝材が1質量%より少なく含有されると、サイクル特性が悪くなる。 By containing 1% by mass to 20% by mass of the buffer material, a negative electrode having a high capacity and excellent cycle characteristics can be obtained. If the buffer material is contained in an amount of more than 20% by mass, the content of the active material is reduced and the battery capacity is reduced. On the other hand, if the buffer material is contained in an amount of less than 1% by mass, the cycle characteristics deteriorate.
ここで、図1を用いて活物質層を説明する。図1は、活物質2と、緩衝材3と、導電材4とがバインダー5を介して集電体1上に、固定され、集電体1上に活物質層6が形成されている模式図である。 Here, the active material layer will be described with reference to FIG. FIG. 1 is a schematic diagram in which an active material 2, a buffer material 3, and a conductive material 4 are fixed on a current collector 1 through a binder 5, and an active material layer 6 is formed on the current collector 1. FIG.
この図1に示すように、得られた活物質層6には緩衝材3が分散しており、緩衝材3は充放電時のLiの吸蔵・放出に伴う体積変化を吸収して活物質2の剥離、脱落を抑制していると考えられる。 As shown in FIG. 1, a buffer material 3 is dispersed in the obtained active material layer 6, and the buffer material 3 absorbs a volume change associated with insertion / extraction of Li during charge / discharge, and thereby the active material 2. It is thought that exfoliation and drop-off are suppressed.
本発明のリチウムイオン二次電池用負極の製造方法は、集電体の表面に、ポリイミド樹脂あるいはアルコキシル基含有シラン変性ポリアミック酸樹脂からなるバインダー樹脂と、Siおよび/またはSnを含む活物質と、導電材と、球状シリコーンゴム粉体にシリコーンレジンを被覆したシリコーン複合粉体からなる緩衝材とを塗布する塗布工程と、集電体に塗布されたバインダー樹脂を150℃以上300℃以下で硬化して活物質、導電材及び緩衝材を集電体表面に固定する硬化工程と、を有する。 In the method for producing a negative electrode for a lithium ion secondary battery of the present invention, a binder resin comprising a polyimide resin or an alkoxyl group-containing silane-modified polyamic acid resin on the surface of the current collector, and an active material containing Si and / or Sn, Applying a conductive material and a buffer material made of a silicone composite powder obtained by coating a silicone resin on a spherical silicone rubber powder, and curing the binder resin applied to the current collector at 150 ° C. or more and 300 ° C. or less. And a curing step for fixing the active material, the conductive material and the buffer material to the surface of the current collector.
バインダー樹脂にポリイミド樹脂あるいはアルコキシル基含有シラン変性ポリアミック酸樹脂を用いることにより、ポリイミド骨格を有するバインダー樹脂とすることが出来る。 By using a polyimide resin or an alkoxyl group-containing silane-modified polyamic acid resin as the binder resin, a binder resin having a polyimide skeleton can be obtained.
バインダーがポリイミド骨格を持つため、バインダーの強度が強く耐熱性及び耐久性に優れる。 Since the binder has a polyimide skeleton, the binder has high strength and excellent heat resistance and durability.
またアルコキシル基含有シラン変性ポリアミック酸樹脂は、樹脂とシリカのハイブリッド体であり、無機成分である集電体や活物質、導電材及び緩衝材とも密着性がよい。そのため、アルコキシル基含有シラン変性ポリイミド樹脂硬化物は、集電体に活物質、導電材等を強固に保持できる。 The alkoxyl group-containing silane-modified polyamic acid resin is a hybrid of resin and silica, and has good adhesion to current collectors, active materials, conductive materials, and buffer materials, which are inorganic components. Therefore, the alkoxy group-containing silane-modified polyimide resin cured product can firmly hold an active material, a conductive material, and the like on the current collector.
上記硬化工程において、バインダー樹脂は150℃以上300℃以下で硬化される。この温度範囲とすることによって、緩衝材を粉体形状としたままでバインダー樹脂を硬化することが出来る。 In the curing step, the binder resin is cured at 150 ° C. or higher and 300 ° C. or lower. By setting it as this temperature range, binder resin can be hardened | cured with the buffer material being a powder form.
また、バインダー樹脂としてのポリイミド樹脂あるいはアルコキシル基含有シラン変性ポリアミック酸樹脂はアミド酸基を有する。アミド酸基を有するこれらのバインダー樹脂は、150℃以上で加熱されることにより、アミド酸基がイミド化される。この時、硬化温度が、通常アミド酸基で推奨される硬化温度400℃よりも低い範囲の温度であってもバインダー樹脂を硬化させることが出来る。 The polyimide resin or the alkoxyl group-containing silane-modified polyamic acid resin as the binder resin has an amic acid group. These binder resins having an amic acid group are imidized by being heated at 150 ° C. or higher. At this time, the binder resin can be cured even when the curing temperature is in a range lower than the curing temperature of 400 ° C. usually recommended for amic acid groups.
また、緩衝材であるシリコーン複合粉体は−50℃〜300℃の範囲でゴム弾性を示すと考えられる。 Moreover, it is thought that the silicone composite powder which is a buffer material shows rubber elasticity in the range of -50 degreeC-300 degreeC.
従って上記硬化工程において温度範囲を150℃以上300℃以下、さらに好ましくは200℃以上300℃以下とすることが、サイクル特性を向上する点で好ましい。 Therefore, in the curing step, it is preferable that the temperature range is 150 ° C. or higher and 300 ° C. or lower, more preferably 200 ° C. or higher and 300 ° C. or lower in terms of improving cycle characteristics.
このような製造方法によれば、活物質が集電体表面から剥離、脱落するのを抑制できる。そのため、サイクル特性に優れたリチウムイオン二次電池用負極を製造することが出来る。 According to such a manufacturing method, it can suppress that an active material peels and drops | omits from the collector surface. Therefore, the negative electrode for lithium ion secondary batteries excellent in cycle characteristics can be manufactured.
本発明のリチウムイオン二次電池用負極とすることによって、優れたサイクル特性を発揮することが出来る。 By using the negative electrode for a lithium ion secondary battery of the present invention, excellent cycle characteristics can be exhibited.
本発明のリチウムイオン二次電池用負極は、集電体と、集電体の表面に固定させた活物質層を有する。活物質層は、活物質、バインダー、導電材、及び緩衝材を含み、活物質はSiおよび/またはSnを含み、緩衝材は球状シリコーンゴム粉体にシリコーンレジンを被覆したシリコーン複合粉体からなる。 The negative electrode for a lithium ion secondary battery of the present invention has a current collector and an active material layer fixed to the surface of the current collector. The active material layer includes an active material, a binder, a conductive material, and a buffer material. The active material includes Si and / or Sn. The buffer material is formed of a silicone composite powder in which a silicone resin is coated on a spherical silicone rubber powder. .
集電体とは放電或いは充電の間、電極に電流を流し続けるための化学的に不活性な電子高伝導体のことである。集電体は電子高伝導体で形成された箔、板等の形状となる。目的に応じた形状であれば特に限定されない。例えば、集電体として銅箔やアルミニウム箔などがあげられる。 A current collector is a chemically inert electronic high conductor that keeps current flowing through an electrode during discharging or charging. The current collector is in the form of a foil, a plate or the like formed of an electronic high conductor. If it is the shape according to the objective, it will not specifically limit. For example, examples of the current collector include copper foil and aluminum foil.
活物質とは、充電反応及び放電反応などの電極反応に直接寄与する物質のことである。本発明の活物質は、リチウムを挿入、脱離可能なSiおよび/またはSnである。 An active material is a substance that directly contributes to electrode reactions such as charge reaction and discharge reaction. The active material of the present invention is Si and / or Sn capable of inserting and extracting lithium.
SiおよびSnは粉体形状であり、バインダー樹脂を介して集電体の表面に塗布され固定される。SiおよびSnの粉体粒子径は100μm以下が好ましい。また、SiおよびSnの粉体粒子径は、0.05μm以上10μm以下がより好ましい。さらに活物質と緩衝材とが同程度の大きさであることが、活物質の体積変化を緩和するのに好ましいため、SiおよびSnの粉体粒子径は、1μm以上10μm以下がより好ましく、1μm〜5μmが更に好ましい。 Si and Sn are in a powder form, and are applied and fixed to the surface of the current collector via a binder resin. The powder particle diameter of Si and Sn is preferably 100 μm or less. The powder particle diameters of Si and Sn are more preferably 0.05 μm or more and 10 μm or less. Furthermore, since it is preferable to reduce the volume change of the active material that the active material and the buffer material have the same size, the powder particle diameter of Si and Sn is more preferably 1 μm or more and 10 μm or less, and 1 μm. More preferably, ˜5 μm.
一般的に負極の活物質に用いられるカーボンの理論容量が372mAhg−1であるのに対し、Siの理論容量は4200mAhg−1、Snは994mAhg−1である。このように従来用いられるカーボンに比べてSi及びSnは大容量の理論容量を有する。 In general, the theoretical capacity of carbon used for the active material of the negative electrode is 372 mAhg −1 , whereas the theoretical capacity of Si is 4200 mAhg −1 and Sn is 994 mAhg −1 . Thus, Si and Sn have a large theoretical capacity as compared with conventionally used carbon.
ただし、カーボン系材料に比べてSi、Snはリチウムの挿入に伴う体積変化が2倍以上ある。具体的には、Si、Snの場合、リチウムの挿入によって体積はもとの体積の約4倍となる。 However, Si and Sn have a volume change more than twice as much as insertion of lithium as compared with carbon-based materials. Specifically, in the case of Si and Sn, the volume becomes about four times the original volume due to the insertion of lithium.
導電材としては炭素質微粒子であるカーボンブラック、黒鉛、アセチレンブラック、ケッチンブラック、カーボンファイバ等を単独で又は二種以上組み合わせて添加することが出来る。 As the conductive material, carbon black, graphite, acetylene black, kettin black, carbon fiber, etc., which are carbonaceous fine particles, can be added alone or in combination of two or more.
緩衝材としては球状シリコーンゴム粉体にシリコーンレジンを被覆したシリコーン複合粉体を用いる。シリコーンとは、シロキサン結合:−Si(R1R2)−O−を骨格とし、これに有機の基R1、R2としてメチル基、ビニル基やフェニル基などが結合している有機珪素化合物のポリマーオルガノポリシロキサンの総称である。シリコーンはその分子量によって低分子量のシリコーン油からシリコーングリース、シリコーンゴム、シリコーンレジンに分類される。 As the buffer material, a silicone composite powder obtained by coating a silicone resin on a spherical silicone rubber powder is used. Silicone is an organosilicon compound having a siloxane bond: —Si (R 1 R 2 ) —O— as a skeleton, and an organic group R 1 , R 2 having a methyl group, a vinyl group, a phenyl group, or the like bonded thereto. It is a general term for the polymer organopolysiloxane. Silicones are classified according to their molecular weights from low molecular weight silicone oils to silicone greases, silicone rubbers, and silicone resins.
球状シリコーンゴム粉体は、直鎖状のジメチルポリシロキサンを架橋した構造を持つシリコーンゴムの微粉末である。他のゴムに比較して耐熱性、耐寒性、耐光性に優れ−50℃〜250℃の広い温度範囲でゴム弾性を示す。 The spherical silicone rubber powder is a fine powder of silicone rubber having a structure in which linear dimethylpolysiloxane is crosslinked. It has excellent heat resistance, cold resistance and light resistance compared to other rubbers, and exhibits rubber elasticity in a wide temperature range of -50 ° C to 250 ° C.
直鎖状のジメチルポリシロキサンを架橋した構造として、分子構造式中に一般式:−(R3 2SiO)a−で示される線状ポリオルガノシロキサンのブロックが挙げられる。ここでR3は、メチル、エチル、プロピル、ブチル、ペンチル、ヘキシル、ヘプチル、オクチル、デシル、ドデシル、テトラデシル、ヘキサデシル、オクタデシル等のアルキル基;シクロペンチル、シクロヘキシル、シクロオクチル等のシクロアルキル基;フェニル、トリル等のアリール基などから選択される一種または二種以上の炭素原子数1〜20からなる一価の有機基あるいはこれらの炭素原子に結合した水素原子の一部をハロゲン原子で置換された一価有機基などから選択されるが、その90モル%以上がメチル基であることが好ましい。またaは5未満では表面平滑性に乏しいものとなり、5,000を超えるものは製造が困難であるので、aは5〜5,000、好ましくは10〜1,000である。 Examples of the structure obtained by crosslinking linear dimethylpolysiloxane include a block of a linear polyorganosiloxane represented by the general formula: — (R 3 2 SiO) a — in the molecular structural formula. R 3 represents an alkyl group such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, decyl, dodecyl, tetradecyl, hexadecyl, octadecyl; a cycloalkyl group such as cyclopentyl, cyclohexyl, cyclooctyl; phenyl, One or two or more monovalent organic groups having 1 to 20 carbon atoms selected from aryl groups such as tolyl, etc., or one in which a part of hydrogen atoms bonded to these carbon atoms is substituted with a halogen atom The organic group is selected from valent organic groups, and 90 mol% or more of them is preferably a methyl group. If a is less than 5, the surface smoothness is poor, and if it exceeds 5,000, it is difficult to produce. Therefore, a is 5 to 5,000, preferably 10 to 1,000.
本発明に用いられるシリコーン複合粉体は、この球状シリコーンゴム粉体にシリコーンレジンを被覆したものである。 The silicone composite powder used in the present invention is obtained by coating the spherical silicone rubber powder with a silicone resin.
シリコーンレジンはSi−O結合が三次元網目状に架橋した構造を持ち、とりわけ耐熱性に優れ、400℃でも重量変化がほとんどなく、熱溶融もせず、多くの有機溶剤に膨潤、溶解しない。このシリコーンレジンとしてポリオルガノシルセスキオキサン樹脂が挙げられる。 Silicone resins have a structure in which Si—O bonds are crosslinked in a three-dimensional network, are particularly excellent in heat resistance, hardly change in weight even at 400 ° C., do not melt by heat, and do not swell or dissolve in many organic solvents. Examples of the silicone resin include polyorganosilsesquioxane resin.
このポリオルガノシルセスキオキサン樹脂は、一般式:R4SiO3/2で示されるシロキサン単位を構成単位とする固形の樹脂重合物である。ここで、R4はメチル、エチル、プロピル、ブチル、ペンチル、ヘキシル、ヘプチル、オクチル、デシル、ドデシル、テトラデシル、ヘキサデシル、オクタデシル等のアルキル基;シクロペンチル、シクロヘキシル、シクロオクチル等のシクロアルキル基;フェニル、トリル等のアリール基などから選択される一種または二種以上の炭素原子数1〜20からなる一価の有機基あるいはこれらの炭素原子に結合した水素原子の一部をハロゲン原子で置換された一価有機基から選択されるが、その90モル%以上がメチル基であることが好ましい。 This polyorganosilsesquioxane resin is a solid resin polymer having a siloxane unit represented by the general formula: R 4 SiO 3/2 as a structural unit. Here, R 4 is an alkyl group such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, decyl, dodecyl, tetradecyl, hexadecyl, octadecyl; a cycloalkyl group such as cyclopentyl, cyclohexyl, cyclooctyl; phenyl, One or two or more monovalent organic groups having 1 to 20 carbon atoms selected from aryl groups such as tolyl, etc., or one in which a part of hydrogen atoms bonded to these carbon atoms is substituted with a halogen atom Although it is selected from valent organic groups, it is preferable that 90 mol% or more thereof is a methyl group.
このような球状シリコーンゴム粉体にシリコーンレジンが被覆されたシリコーン複合粉体の製法は、例えば球状シリコーンゴム粉体の水分散液をアルカリ性に保持し、シリコーンレジンを加水分解、縮合させることで球状シリコーンゴム粉体の表面にシリコーンレジンを被覆することができる。 A method for producing a silicone composite powder in which a silicone resin is coated on such a spherical silicone rubber powder is, for example, a method in which an aqueous dispersion of a spherical silicone rubber powder is kept alkaline, and the silicone resin is hydrolyzed and condensed to form spherical particles. A silicone resin can be coated on the surface of the silicone rubber powder.
このようなシリコーン複合粉体は、耐熱性、耐寒性、耐衝撃性、潤滑性に優れている。また、シリコーン複合粉体は、−50℃〜300℃の広い温度範囲でゴム弾性を示すと考えられる。シリコーン複合粉体は、表面をシリコーンレジンで被覆しているため、球状シリコーンゴム粉体に比べて分散性がよく、活物質層に良好に分散できる。また、シリコーンレジンは球状シリコーンゴム粉体に比べて耐熱性が高いため、シリコーン複合粉体はゴム弾性を示す温度範囲が球状シリコーンゴム粉体より上がると考えられる。 Such a silicone composite powder is excellent in heat resistance, cold resistance, impact resistance, and lubricity. Further, the silicone composite powder is considered to exhibit rubber elasticity in a wide temperature range of −50 ° C. to 300 ° C. Since the surface of the silicone composite powder is coated with a silicone resin, the silicone composite powder has better dispersibility than the spherical silicone rubber powder and can be well dispersed in the active material layer. Further, since the silicone resin has higher heat resistance than the spherical silicone rubber powder, it is considered that the temperature range in which the silicone composite powder exhibits rubber elasticity is higher than that of the spherical silicone rubber powder.
上記シリコーン複合粉体は、シリコーン複合パウダーの名称でKMP−600、KMP−601、KMP−602、KMP−605、X−52−7030として信越化学工業(株)より市販されている。 The silicone composite powder is commercially available from Shin-Etsu Chemical Co., Ltd. as KMP-600, KMP-601, KMP-602, KMP-605, and X-52-7030 under the name of silicone composite powder.
活物質層の総量を100質量%としたときに、上記緩衝材は1質量%〜20質量%含有されることが好ましい。上記緩衝材を1質量%〜20質量%含有することにより、高容量かつサイクル特性が優れる負極とすることが出来る。 When the total amount of the active material layer is 100% by mass, the buffer material is preferably contained in an amount of 1% by mass to 20% by mass. By containing the buffer material in an amount of 1% by mass to 20% by mass, a negative electrode having a high capacity and excellent cycle characteristics can be obtained.
また、シリコーン複合粉体の粒径は、望ましくは1μm〜10μm、より望ましくは1μm〜5μmである。SiやSnの体積変化を緩和するためには、シリコーン複合粉体の粒径は、SiやSnと同程度の大きさが望ましい。シリコーン複合粉体の粒径が、SiやSnの粒径よりも小さすぎると緩衝効果が少なくなり、また大きすぎると電極全体にシリコーン複合粉体が行き渡らずに緩衝効果が期待できなくなる。 The particle size of the silicone composite powder is desirably 1 μm to 10 μm, more desirably 1 μm to 5 μm. In order to mitigate the volume change of Si and Sn, the particle size of the silicone composite powder is desirably as large as that of Si or Sn. If the particle size of the silicone composite powder is too smaller than the particle size of Si or Sn, the buffering effect is reduced. If the particle size is too large, the silicone composite powder does not reach the entire electrode and the buffering effect cannot be expected.
これらの活物質、導電材、緩衝材はバインダーを介して集電体に固定される。 These active material, conductive material, and buffer material are fixed to the current collector through a binder.
バインダーは、特に制限されないが、ポリイミド樹脂硬化物あるいはアルコキシル基含有シラン変性ポリイミド樹脂硬化物を含むことが好ましい。 The binder is not particularly limited, but preferably contains a cured polyimide resin or a cured silane-modified polyimide resin containing an alkoxyl group.
バインダーにポリイミド樹脂硬化物あるいはアルコキシル基含有シラン変性ポリイミド樹脂硬化物を用いることにより、ポリイミド骨格を有するバインダーとすることが出来る。 By using a polyimide resin cured product or an alkoxyl group-containing silane-modified polyimide resin cured product as the binder, a binder having a polyimide skeleton can be obtained.
バインダーがポリイミド骨格を持つため、バインダーの強度が強く耐熱性及び耐久性に優れる。また、アルコキシル基含有シラン変性ポリイミド樹脂硬化物は、樹脂とシリカのハイブリッド体であり、無機成分である集電体や活物質、導電材及び緩衝材とも密着性がよく、集電体に活物質等を強固に保持できる。 Since the binder has a polyimide skeleton, the binder has high strength and excellent heat resistance and durability. Further, the cured product of the alkoxyl group-containing silane-modified polyimide resin is a hybrid of resin and silica, and has good adhesion to the current collector and active material, conductive material and buffer material, which are inorganic components, and the current collector has an active material. Etc. can be held firmly.
また、本発明のリチウムイオン二次電池用負極の製造方法は、塗布工程と硬化工程とを有する。 Moreover, the manufacturing method of the negative electrode for lithium ion secondary batteries of this invention has an application | coating process and a hardening process.
塗布するとは集電体にバインダー樹脂、活物質、導電材及び緩衝材を載せることである。塗布方法として、ロールコート法、ディップコート法、ドクターブレード法、スプレーコート法、カーテンコート法など二次電池用電極を作製する際に一般的に用いる塗布方法を用いることが出来る。 Applying means placing a binder resin, an active material, a conductive material and a buffer material on the current collector. As a coating method, a coating method generally used when producing an electrode for a secondary battery, such as a roll coating method, a dip coating method, a doctor blade method, a spray coating method, or a curtain coating method, can be used.
バインダー樹脂はこれらの活物質、導電材及び緩衝材を集電体に塗布する際の結着剤として用いられる。バインダー樹脂はなるべく少ない量で活物質等を結着させることが求められ、その量は活物質、導電材、緩衝材及びバインダー樹脂を合計したものの0.5wt%〜50wt%が望ましい。
本発明で用いるバインダー樹脂は、ポリイミド樹脂あるいはアルコキシル基含有シラン変性ポリアミック酸樹脂が好ましい。
The binder resin is used as a binder when these active materials, conductive materials and buffer materials are applied to the current collector. The binder resin is required to bind the active material or the like in as little amount as possible, and the amount is preferably 0.5 wt% to 50 wt% of the total of the active material, the conductive material, the buffer material, and the binder resin.
The binder resin used in the present invention is preferably a polyimide resin or an alkoxyl group-containing silane-modified polyamic acid resin.
アルコキシル基含有シラン変性ポリアミック酸樹脂は樹脂とシリカとのハイブリッド体となっている。樹脂とシリカとのハイブリッド体であることによって無機成分である集電体や活物質及び導電材とも密着性がよく、集電体に活物質や導電材を強固に保持出来る。 The alkoxyl group-containing silane-modified polyamic acid resin is a hybrid of resin and silica. By being a hybrid of resin and silica, the current collector, active material, and conductive material, which are inorganic components, have good adhesion, and the current collector can hold the active material and conductive material firmly.
上記バインダー樹脂は公知の技術によって合成することが出来る。例えば、バインダー樹脂としてアルコキシ基含有シラン変性ポリアミック酸樹脂とする場合、前駆体であるカルボン酸無水物成分とジアミン成分とからなるポリアミック酸と、アルコキシシラン部分縮合物とを反応させて形成することができる。アルコキシシラン部分縮合物は加水分解性アルコキシシランモノマーを、酸又は塩基触媒、及び水の存在下で部分的に縮合させて得られるものが用いられる。この時、アルコキシシラン部分縮合物はあらかじめエポキシ化合物と反応させ、エポキシ基含有アルコキシシラン部分縮合物としてからポリアミック酸と反応させてアルコキシ基含有シラン変性ポリアミック酸樹脂を形成してもよい。 The binder resin can be synthesized by a known technique. For example, when an alkoxy group-containing silane-modified polyamic acid resin is used as the binder resin, it can be formed by reacting a polyamic acid composed of a carboxylic acid anhydride component and a diamine component as a precursor with an alkoxysilane partial condensate. it can. The alkoxysilane partial condensate is obtained by partially condensing a hydrolyzable alkoxysilane monomer in the presence of an acid or base catalyst and water. At this time, the alkoxysilane partial condensate may be reacted with an epoxy compound in advance to form an epoxy group-containing alkoxysilane partial condensate and then reacted with a polyamic acid to form an alkoxy group-containing silane-modified polyamic acid resin.
また、上記のバインダー樹脂は、市販品を好適に用いることが出来る。例えば、アルコキシ基含有シラン変性ポリアミック酸樹脂である商品名「コンポセランH800」(荒川化学工業社製)の市販品がある。 Moreover, a commercial item can be used suitably for said binder resin. For example, there is a commercial product under the trade name “COMPOCERAN H800” (Arakawa Chemical Industries, Ltd.), which is an alkoxy group-containing silane-modified polyamic acid resin.
上記商品名「コンポセランH800」(荒川化学工業社製)の基本骨格の化学式を下記に示す。 The chemical formula of the basic skeleton of the above-mentioned trade name “COMPOCERAN H800” (manufactured by Arakawa Chemical Industries) is shown below.
導電材としては炭素質微粒子であるカーボンブラック、黒鉛、アセチレンブラック、ケッチンブラック、カーボンファイバ等を単独で又は二種以上組み合わせて添加することが出来る。 As the conductive material, carbon black, graphite, acetylene black, kettin black, carbon fiber, etc., which are carbonaceous fine particles, can be added alone or in combination of two or more.
塗布工程はバインダー樹脂と活物質と導電材と緩衝材とをあらかじめ混合し、溶媒等を加えてスラリーとしてから集電体に塗布することが出来る。塗布厚みは10μm〜100μmが好ましい。 In the coating step, a binder resin, an active material, a conductive material, and a buffer material are mixed in advance, and a solvent or the like is added to form a slurry, which can be applied to the current collector. The coating thickness is preferably 10 μm to 100 μm.
また、バインダー樹脂と活物質と導電材と緩衝材との混合割合は質量部(wt%)で活物質:緩衝材:導電材:バインダー樹脂=79:1:5:15〜60:20:5:15が好ましい。なお、この混合割合は、それぞれの上限および下限を示している。例えば、活物質の場合、上限は79wt%、下限は60wt%である。言い換えると、活物質と緩衝材とをあわせたものを100質量部とすると、活物質は75〜99質量部、緩衝材は1〜25質量部であることが好ましい。 In addition, the mixing ratio of the binder resin, the active material, the conductive material, and the buffer material is part by mass (wt%), and the active material: buffer material: conductive material: binder resin = 79: 1: 5: 15-60: 20: 5. : 15 is preferable. In addition, this mixing ratio has shown the upper limit and the minimum of each. For example, in the case of an active material, the upper limit is 79 wt% and the lower limit is 60 wt%. In other words, when the total of the active material and the buffer material is 100 parts by mass, the active material is preferably 75 to 99 parts by mass, and the buffer material is preferably 1 to 25 parts by mass.
硬化工程はバインダー樹脂を硬化する工程である。その際、硬化条件は、バインダー樹脂が硬化し、かつシリコーン複合粉体である緩衝材の粉体形状を維持し、シリコーン複合粉体がゴム弾性を示す硬化条件であることが必要である。 The curing step is a step of curing the binder resin. At that time, the curing conditions are required to be a curing condition in which the binder resin is cured and the powder shape of the buffer material which is the silicone composite powder is maintained, and the silicone composite powder exhibits rubber elasticity.
バインダー樹脂としてポリイミド樹脂あるいはアルコキシル基含有シラン変性ポリアミック酸樹脂を用いた場合は、活物質などを塗布された集電体を150℃以上300℃以下で加熱する。 When a polyimide resin or an alkoxyl group-containing silane-modified polyamic acid resin is used as the binder resin, the current collector coated with the active material is heated at 150 ° C. or higher and 300 ° C. or lower.
この硬化条件で硬化することによって、シリコーン複合粉体はその形状及びゴム弾性を保持し、緩衝材として機能すると考えられる。 By curing under these curing conditions, it is considered that the silicone composite powder retains its shape and rubber elasticity and functions as a buffer material.
またこれらのバインダー樹脂はアミド酸基を有する。アミド酸基は加熱処理することにより、イミド化(脱水重合)してイミド基が形成される。このイミド化反応は150℃程度から開始され、200℃以上で進行しやすい。アミド酸のイミド化率は70%以上が望ましく、具体的には、イミド基とアミド酸基を99:1〜70:30の割合で有するまでイミド化することが好ましい。200℃以上でイミド化率が70%以上となる。 These binder resins have an amic acid group. The amic acid group is imidized (dehydration polymerization) by heat treatment to form an imide group. This imidization reaction starts from about 150 ° C. and easily proceeds at 200 ° C. or higher. The imidation ratio of the amic acid is desirably 70% or more. Specifically, it is preferable to imidize until having an imide group and an amic acid group in a ratio of 99: 1 to 70:30. The imidation ratio becomes 70% or more at 200 ° C or higher.
従って上記温度範囲内にあれば、バインダーとして十分機能し、負極のサイクル特性を良好に維持出来る。 Therefore, if it exists in the said temperature range, it fully functions as a binder and can maintain the cycling characteristics of a negative electrode favorably.
以下、一実施例を挙げて本発明を更に詳しく説明する。 Hereinafter, the present invention will be described in more detail with reference to an example.
本発明のリチウムイオン二次電池用負極を以下のように作製し、評価用モデル電池を用いて充放電効率試験及びサイクル試験を行った。試験は負極を評価極とした、ラミネート型のリチウムイオン二次電池を用いた。 A negative electrode for a lithium ion secondary battery of the present invention was prepared as follows, and a charge / discharge efficiency test and a cycle test were performed using a model battery for evaluation. The test used a laminate-type lithium ion secondary battery with the negative electrode as the evaluation electrode.
<評価用電極作製>
活物質として、Si粉末を用い、バインダー樹脂として[化2]に示した構造を有するアルコキシ含有シラン変性ポリアミック酸樹脂(溶剤組成:N,N−ジメチルアセトアミド(DMAc)、硬化残分15.1%、粘度5100mPa・s/25℃、硬化残分中のシリカ、2wt%)を用いて電極を作製した。
<Production of electrode for evaluation>
An Si-containing powder is used as the active material, and an alkoxy-containing silane-modified polyamic acid resin having the structure shown in [Chemical Formula 2] as the binder resin (solvent composition: N, N-dimethylacetamide (DMAc), curing residue 15.1% , A viscosity of 5100 mPa · s / 25 ° C., silica in the cured residue, 2 wt%) to prepare an electrode.
この時、緩衝材として平均粒径5μmの粉体であるシリコーン複合パウダー(KMP−600、信越化学工業(株))を用いた。また導電材としてカーボン系導電助剤を用い、具体的にはケッチェンブラックインターナショナル社製のKB(ケッチンブラック)と黒鉛等の2〜3種類を混ぜて用いた。 At this time, a silicone composite powder (KMP-600, Shin-Etsu Chemical Co., Ltd.), which is a powder having an average particle size of 5 μm, was used as a buffer material. Further, a carbon-based conductive additive was used as the conductive material, and specifically, a mixture of two or three types such as KB (ketine black) manufactured by Ketjen Black International and graphite was used.
Si粉末は、最大粒子径10μm以下で平均粒子径2μmのSi粒子(福田金属箔粉工業製)をそのまま使用した。 As the Si powder, Si particles having a maximum particle diameter of 10 μm or less and an average particle diameter of 2 μm (manufactured by Fukuda Metal Foil Powder Industry) were used as they were.
実施例1および比較例2として、Si:シリコーン複合パウダー:カーボン系導電助剤:バインダー樹脂(アルコキシ含有シラン変性ポリアミック酸樹脂)=60:5:20:15(wt%)の割合で混合した。比較例1として、緩衝材を用いないで、Si:カーボン系導電助剤:バインダー樹脂(アルコキシ含有シラン変性ポリアミック酸樹脂)=60:25:15(wt%)の割合で混合した。 As Example 1 and Comparative Example 2, Si: silicone composite powder: carbon-based conductive additive: binder resin (alkoxy-containing silane-modified polyamic acid resin) = 60: 5: 20: 15 (wt%). As Comparative Example 1, Si: carbon-based conductive auxiliary agent: binder resin (alkoxy-containing silane-modified polyamic acid resin) = 60: 25: 15 (wt%) was mixed without using a buffer material.
実施例1ではアルコキシ含有シラン変性ポリアミック酸樹脂をN-メチルピロリドン(NMP)に溶解させたペースト15wt%に、Si粉末60wt%及びシリコーン複合パウダー5wt%を入れ、さらにカーボン系導電助剤20wt%を添加し、混合してスラリ−を調製した。比較例1および比較例2も同様の操作でスラリーを調整した。 In Example 1, 60 wt% Si powder and 5 wt% silicone composite powder were added to 15 wt% of a paste prepared by dissolving an alkoxy-containing silane-modified polyamic acid resin in N-methylpyrrolidone (NMP), and further 20 wt% of a carbon-based conductive additive was added. A slurry was prepared by adding and mixing. In Comparative Examples 1 and 2, the slurry was prepared by the same operation.
スラリー調整後、厚さ18μmの電解銅箔に上記スラリ−を乗せて、ドクターブレードを用いて銅箔上に成膜した。 After slurry adjustment, the slurry was placed on an electrolytic copper foil having a thickness of 18 μm, and a film was formed on the copper foil using a doctor blade.
得られたシートを80℃で20分間乾燥してNMPを揮発させて除去した後、ロ−ルプレス機により、電解銅箔からなる集電体と上記複合粉体からなる負極層を強固に密着接合させた。 After the obtained sheet was dried at 80 ° C. for 20 minutes to volatilize and remove NMP, the current collector made of electrolytic copper foil and the negative electrode layer made of the above composite powder were firmly adhered and bonded by a roll press machine. I let you.
これを所定の形状に打ち抜き、実施例1及び比較例1は、200℃で3時間、加熱硬化させて厚さ25μm程度の電極とした。また比較例2は430℃で10分、加熱硬化させて厚さ25μm程度の電極とした。 This was punched into a predetermined shape, and Example 1 and Comparative Example 1 were heated and cured at 200 ° C. for 3 hours to form an electrode having a thickness of about 25 μm. In Comparative Example 2, an electrode having a thickness of about 25 μm was obtained by heating and curing at 430 ° C. for 10 minutes.
なおシリコーン複合パウダーは、200℃の熱処理ではその形状が変化しない。 The shape of the silicone composite powder does not change by heat treatment at 200 ° C.
それを示すために、実施例1の電極のSEM写真と比較例2の電極のSEM写真を図4の(a)(b)に示す。この時、実施例1のアルコキシ含有シラン変性ポリアミック酸樹脂はイミド化率が80%程度であった。 In order to show this, an SEM photograph of the electrode of Example 1 and an SEM photograph of the electrode of Comparative Example 2 are shown in FIGS. At this time, the imidation ratio of the alkoxy-containing silane-modified polyamic acid resin of Example 1 was about 80%.
図4の(a)に示す実施例1のSEM写真に丸印で示すように、実施例1の200℃熱処理品においてはシリコーン複合パウダーが、形状に変化なく残っていることがわかった。それに対して図4の(b)に示す比較例2の430℃処理品のSEM写真では、シリコーン複合パウダーが消失し、空隙(図4の(b)に示される黒い丸い部分)が観察された。 As indicated by a circle in the SEM photograph of Example 1 shown in FIG. 4A, it was found that the silicone composite powder remained unchanged in the 200 ° C. heat-treated product of Example 1. On the other hand, in the SEM photograph of the 430 ° C. treated product of Comparative Example 2 shown in FIG. 4 (b), the silicone composite powder disappeared and voids (the black round parts shown in FIG. 4 (b)) were observed. .
上記で得られた負極の構成を、図5を用いて説明する。図5は、ラミネートセルの極板群の構成を示す説明図であって、上記の手順で作製した負極は図5の電極11に相当する。 The structure of the negative electrode obtained above will be described with reference to FIG. FIG. 5 is an explanatory diagram showing the configuration of the electrode plate group of the laminate cell, and the negative electrode produced by the above procedure corresponds to the electrode 11 of FIG.
電極11は、銅箔からなるシート状の集電箔12と、集電箔12の表面に形成された負極活物質層13と、からなる。集電箔12は、矩形状(26mm×31mm)の合材塗付部12aと、合材塗付部12aの隅部から延出するタブ溶接部12bと、を備える。合材塗付部12aの一方の面には、負極活物質層13が形成されている。負極活物質層13は、前述したように、Si粉末、カーボン系導電助剤、バインダー、シリコーン複合パウダーを含む。 The electrode 11 includes a sheet-shaped current collector foil 12 made of a copper foil, and a negative electrode active material layer 13 formed on the surface of the current collector foil 12. The current collector foil 12 includes a rectangular (26 mm × 31 mm) composite material coating portion 12a and a tab weld portion 12b extending from a corner of the composite material coating portion 12a. A negative electrode active material layer 13 is formed on one surface of the composite material coating portion 12a. As described above, the negative electrode active material layer 13 includes Si powder, a carbon-based conductive additive , a binder, and a silicone composite powder.
集電箔12のタブ溶接部12bには、ニッケル製のタブ14を抵抗溶接した。さらに、タブ溶接部12bには、樹脂フィルム15を被着した。 A nickel tab 14 was resistance welded to the tab weld 12 b of the current collector foil 12. Furthermore, the resin film 15 was adhered to the tab weld portion 12b.
同様の方法で20μmのアルミニウム箔にLiNi1/3Co1/3Mn1/3O2を正極活物質としてバインダー樹脂PVdFを用いて固定された電極を作成し、厚さ90μm以下の正極とした。 In the same manner, an electrode fixed on a 20 μm aluminum foil using LiNi 1/3 Co 1/3 Mn 1/3 O 2 as a positive electrode active material and a binder resin PVdF was prepared, and a positive electrode having a thickness of 90 μm or less was obtained. .
<ラミネート型電池作製>
上記した電極を負極とし、厚み85μmのLiNi1/3Co1/3Mn1/3O2を正極活物質とした電極を正極とし、1モルのLiPF6/エチレンカ−ボネ−ト(EC)+ジエチルカ−ボネ−ト(DEC)(EC:DEC=1:1(体積比))溶液を電解液として、ラミネート型電池を作製した。
<Production of laminated battery>
The above electrode is used as a negative electrode, an electrode using LiNi 1/3 Co 1/3 Mn 1/3 O 2 having a thickness of 85 μm as a positive electrode active material, and 1 mol of LiPF 6 / ethylene carbonate (EC) + A laminate type battery was produced using a diethyl carbonate (DEC) (EC: DEC = 1: 1 (volume ratio)) solution as an electrolyte.
ラミネート型電池は、電極11、対極16およびセパレータ19が積層されてなる極板群10と、極板群10を包み込んで密閉するラミネートフィルム(図示せず)と、ラミネートフィルム内に注入される非水電解液と、を備える。ラミネートセルの作製手順を、図5を用いて説明する。 The laminate type battery includes an electrode plate group 10 in which an electrode 11, a counter electrode 16 and a separator 19 are laminated, a laminate film (not shown) that wraps and seals the electrode plate group 10, and a non-injection that is injected into the laminate film. A water electrolyte solution. The production procedure of the laminate cell will be described with reference to FIG.
電極11の構成は、既に説明した通りにした。対極16には、正極活物質としてLiNi1/3Co1/3Mn1/3O2を含む正極を用いた。この正極は、集電体として厚さ20μmのアルミニウム箔が用いられ、容量は3.0mAh/cm2、電極密度は2.3g/cm2であった。 The configuration of the electrode 11 was as described above. As the counter electrode 16, a positive electrode containing LiNi 1/3 Co 1/3 Mn 1/3 O 2 as a positive electrode active material was used. In this positive electrode, an aluminum foil having a thickness of 20 μm was used as a current collector, a capacity was 3.0 mAh / cm 2 , and an electrode density was 2.3 g / cm 2 .
対極16は、電極11と同様に、矩形状(25mm×30mm)の合材塗付部16aと、本体部16aの隅部から延出するタブ溶接部16bと、を備え、いずれもアルミニウム箔からなる構成とした。合材塗付部16aの一方の面には、LiNi1/3Co1/3Mn1/3O2を含む正極活物質層を形成した。タブ溶接部16bには、アルミニウム製のタブ17を抵抗溶接した。さらに、タブ溶接部16bには、樹脂フィルム18を被着した。 Like the electrode 11, the counter electrode 16 includes a rectangular (25 mm × 30 mm) composite material coating portion 16a and a tab weld portion 16b extending from a corner of the main body portion 16a, both of which are made of aluminum foil. It became the composition which becomes. A positive electrode active material layer containing LiNi 1/3 Co 1/3 Mn 1/3 O 2 was formed on one surface of the composite material coating portion 16a. An aluminum tab 17 was resistance welded to the tab weld 16b. Further, a resin film 18 was attached to the tab weld 16b.
セパレータ19には、ポリプロピレン樹脂からなる矩形状シート(27mm×32mm、厚さ25μm)を用いた。電極11の合材塗付部12a、セパレータ19、対極16の合材塗付部16aの順に、負極活物質層と正極活物質層とがセパレータ19を介して対向するように積層して、極板群10を構成した。 As the separator 19, a rectangular sheet (27 mm × 32 mm, thickness 25 μm) made of polypropylene resin was used. In this order, the negative electrode active material layer and the positive electrode active material layer are stacked so that the negative electrode active material layer and the positive electrode active material layer face each other through the separator 19 in this order. A plate group 10 was constructed.
次に、極板群10を2枚一組のラミネートフィルムで覆い、三辺をシールした後、袋状となったラミネートフィルムに所定の非水電解液を注入した。その後、残りの一辺をシールすることで、四辺が気密にシールされ、極板群10および非水電解液が密閉されたラミネートセルを得た。なお、両極のタブ14および17の一部は、外部との電気的接続のため外側へ延出している。 Next, the electrode plate group 10 was covered with a set of two laminated films, the three sides were sealed, and then a predetermined nonaqueous electrolyte was poured into the bag-like laminated film. Thereafter, the remaining one side was sealed to obtain a laminate cell in which the four sides were hermetically sealed, and the electrode plate group 10 and the non-aqueous electrolyte were sealed. A part of the poles of the tab 1 4 and 17, extend outwardly for external electrical connection.
<ラミネート型電池評価>
このモデル電池における評価極の評価を次の方法で行った。
<Laminated battery evaluation>
Evaluation of the evaluation electrode in this model battery was performed by the following method.
(充放電効率試験)
下記実施例1及び比較例1の負極を用い、充放電試験を行い充放電効率(%)を計算した。
(Charge / discharge efficiency test)
Using the negative electrodes of Example 1 and Comparative Example 1 below, a charge / discharge test was performed to calculate charge / discharge efficiency (%).
1サイクル目:0.2Cで4.25VまでCCCV充電(定電流定電圧充電)を10時間行った。その後、2.6Vまで0.2Cの一定電流で放電した(0.2C、CC放電(定電流放電))。電流は、4.6mAの定電流とした。 1st cycle: CCCV charge (constant current constant voltage charge) was performed for 10 hours to 4.25V at 0.2C. Thereafter, the battery was discharged at a constant current of 0.2 C up to 2.6 V (0.2 C, CC discharge (constant current discharge)). The current was a constant current of 4.6 mA.
2サイクル目:0.2Cで4.25VまでCCCV充電(定電流定電圧充電)を10時間行った。その後、2.6Vまで1Cの一定電流(23mA)で放電した(1C、CC放電(定電流放電))。 Second cycle: CCCV charging (constant current constant voltage charging) was performed for 10 hours at 0.2C up to 4.25V. Thereafter, the battery was discharged at a constant current (23 mA) of 1 C up to 2.6 V (1 C, CC discharge (constant current discharge)).
充放電効率は以下の式を用いて求めた。 The charge / discharge efficiency was determined using the following equation.
充放電効率(%)=放電容量/充電容量×100
この時、電気容量を1時間で放電する電流を1C、5時間で放電する電流を0.2Cと表す。従って1Cの電流値は0.2Cの電流値の5倍である。
Charging / discharging efficiency (%) = discharge capacity / charge capacity × 100
At this time, the current that discharges the electric capacity in 1 hour is 1 C, and the current that discharges in 5 hours is 0.2 C. Therefore, the current value of 1C is five times the current value of 0.2C.
この1サイクル目と2サイクル目の実施例1及び比較例1の電極を用いたモデル電池の充放電効率を比較するグラフを図2に示す。X軸は上記した電流レートを表し、Y軸に充放電効率(%)を表す。 A graph comparing the charge and discharge efficiencies of the model batteries using the electrodes of Example 1 and Comparative Example 1 in the first and second cycles is shown in FIG. The X axis represents the above-described current rate, and the Y axis represents charge / discharge efficiency (%).
図2から見られるように、実施例1の電極は、1サイクル目(0.2C)で充放電効率が99%、2サイクル目(1C)で93%あり、0.2Cの時約1%、1Cの時約3%も比較例1に比べて充放電効率が高い。つまり実施例1の電極は、比較例1の電極と比べて、充電した容量をしっかりと放電出来ていることがわかった。これは上記シリコーン複合パウダーが緩衝材として働き、活物質であるSi粒子の体積変化を吸収して、バインダーの破壊、しいては活物質の剥離、脱落を防ぐことが出来たためと考えられる。また実施例1は比較例1に比べて、0.2Cより1Cのほうが充放電効率の差が大きく、特に急速充放電時に上記効果が大きいことがわかる。 As can be seen from FIG. 2, the electrode of Example 1 has a charge / discharge efficiency of 99% at the first cycle (0.2C), 93% at the second cycle (1C), and about 1% at 0.2C. As compared with Comparative Example 1, the charge / discharge efficiency is about 3% at 1C. That is, it was found that the electrode of Example 1 was able to discharge the charged capacity more firmly than the electrode of Comparative Example 1. This is thought to be because the silicone composite powder worked as a buffering material and absorbed the volume change of the Si particles as the active material, thereby preventing the binder from being broken and thus preventing the active material from peeling off and falling off. In addition, compared with Comparative Example 1, Example 1 has a larger difference in charge / discharge efficiency at 1C than at 0.2C, and it can be seen that the above-described effect is particularly great during rapid charge / discharge.
(サイクル試験)
充電:0.2Cで4.25VまでCCCV充電(定電流定電圧充電)を10時間行った。放電:2.6Vまで0.2Cの一定電流で放電した(0.2C、CC放電(定電流放電))(1C容量=23mAh)。
(Cycle test)
Charging: CCCV charging (constant current constant voltage charging) was performed for 10 hours to 4.25 V at 0.2 C. Discharge: Discharged at a constant current of 0.2 C up to 2.6 V (0.2 C, CC discharge (constant current discharge)) (1 C capacity = 23 mAh).
これを1サイクルとし、繰り返し充放電を行い、放電容量を調べた。 This was made into 1 cycle, charging / discharging was repeated and discharge capacity was investigated.
実施例1及び比較例1の電極を有するモデル電池について、サイクル数と容量維持率(%)の関係を示すグラフを図3に示す。図3から明らかなように、まず実施例1の電極を評価極とした電池では、比較例1の電極を評価極とした電池に比べて70サイクル目ぐらいから容量の低下率が少なくなった。また比較例1の100サイクル後の容量維持率が55%程度であるのに対し、実施例1では100サイクル後の容量維持率が62%程度維持されていることがわかった。 FIG. 3 shows a graph showing the relationship between the number of cycles and the capacity retention rate (%) for the model batteries having the electrodes of Example 1 and Comparative Example 1. As is clear from FIG. 3, in the battery using the electrode of Example 1 as the evaluation electrode, the rate of decrease in capacity decreased from about the 70th cycle as compared with the battery using the electrode of Comparative Example 1 as the evaluation electrode. Further, it was found that the capacity retention rate after 100 cycles of Comparative Example 1 was about 55%, whereas in Example 1, the capacity retention rate after 100 cycles was maintained at about 62%.
つまり、このサイクル試験結果から実施例1の電極は、比較例1の電極と比べて、サイクル特性が優れていることがわかった。これは上記シリコーン複合パウダーが緩衝材として働き、活物質の剥離、脱落を防ぐことが出来たためと考えられる。また、上記した充放電効率試験結果から、急速充放電時(例えば放電レート1C)の場合にはサイクル試験結果においても、効果がもっと顕著になると思われる。 That is, from the cycle test results, it was found that the electrode of Example 1 had better cycle characteristics than the electrode of Comparative Example 1. This is presumably because the silicone composite powder worked as a cushioning material and prevented the active material from peeling off and falling off. In addition, from the above-described charge / discharge efficiency test results, it is considered that the effect becomes more remarkable even in the cycle test results in the case of rapid charge / discharge (for example, discharge rate 1C).
上記実施例、比較例では、バインダー樹脂としてアルコキシル基含有シラン変性ポリアミック酸樹脂を用いたが、ポリイミド樹脂でも同様の効果が得られる。 In the above Examples and Comparative Examples, an alkoxyl group-containing silane-modified polyamic acid resin was used as the binder resin, but the same effect can be obtained with a polyimide resin.
1:集電体、2:活物質、3:緩衝材、4:導電材、5:バインダー、6:活物質層、
10:極板群、11:電極、16:対極、19:セパレーター。
1: current collector, 2: active material, 3: buffer material, 4: conductive material, 5: binder, 6: active material layer,
10: Electrode plate group, 11: Electrode, 16: Counter electrode, 19: Separator.
Claims (4)
前記活物質層は、活物質、バインダー、導電材、及び緩衝材を含み、
前記活物質はSiおよび/またはSnを含み、
前記緩衝材は球状シリコーンゴム粉体にシリコーンレジンを被覆したシリコーン複合粉体からなることを特徴とするリチウムイオン二次電池用負極。 In the negative electrode for a lithium ion secondary battery having a current collector and an active material layer fixed on the surface of the current collector,
The active material layer includes an active material, a binder, a conductive material, and a buffer material,
The active material contains Si and / or Sn,
The negative electrode for a lithium ion secondary battery, wherein the buffer material is made of a silicone composite powder obtained by coating a silicone resin on a spherical silicone rubber powder.
前記集電体に塗布された前記バインダー樹脂を150℃以上300℃以下で硬化して前記活物質、前記導電材及び前記緩衝材を前記集電体表面に固定する硬化工程と、
を有することを特徴とするリチウムイオン二次電池用負極の製造方法。 The surface of the current collector was coated with a silicone resin on a binder resin made of a polyimide resin or an alkoxyl group-containing silane-modified polyamic acid resin, an active material containing Si and / or Sn, a conductive material, and a spherical silicone rubber powder. An application step of applying a cushioning material made of silicone composite powder;
A curing step of curing the binder resin applied to the current collector at 150 ° C. or more and 300 ° C. or less to fix the active material, the conductive material, and the buffer material to the current collector surface;
The manufacturing method of the negative electrode for lithium ion secondary batteries characterized by having.
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JP2009220519A JP5035313B2 (en) | 2009-09-25 | 2009-09-25 | Negative electrode for lithium ion secondary battery and method for producing the same |
PCT/JP2010/065447 WO2011037013A1 (en) | 2009-09-25 | 2010-09-01 | Anode for use in a lithium-ion secondary battery, and manufacturing method therefor |
EP14164918.6A EP2762523A1 (en) | 2009-09-25 | 2010-09-01 | Lithium-ion secondary battery comprising a binder |
EP10818689.1A EP2482369A4 (en) | 2009-09-25 | 2010-09-01 | Anode for use in a lithium-ion secondary battery, and manufacturing method therefor |
US13/497,717 US8822083B2 (en) | 2009-09-25 | 2010-09-01 | Negative electrode for lithium-ion secondary battery and manufacturing process for the same |
KR1020127005778A KR101294228B1 (en) | 2009-09-25 | 2010-09-01 | Negative electrode for lithium-ion secondary battery and manufacturing process for the same |
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JP2012221824A (en) * | 2011-04-12 | 2012-11-12 | Sony Corp | Lithium ion secondary battery, electronic apparatus, electric tool, electric vehicle and power storage system |
WO2012153469A1 (en) * | 2011-05-12 | 2012-11-15 | 株式会社豊田自動織機 | Electrode for lithium ion secondary batteries, method for producing same and lithium ion secondary battery using electrode for lithium ion secondary batteries |
WO2013114788A1 (en) * | 2012-02-02 | 2013-08-08 | Jsr株式会社 | Method for producing electrode for electricity storage devices |
JP2013175315A (en) * | 2012-02-24 | 2013-09-05 | Toyota Industries Corp | Lithium ion secondary battery, and vehicle |
JP2013191331A (en) * | 2012-03-13 | 2013-09-26 | Toyota Industries Corp | Nonaqueous electrolyte secondary battery and vehicle |
JP5525003B2 (en) | 2012-05-07 | 2014-06-18 | 古河電気工業株式会社 | Anode for non-aqueous electrolyte secondary battery and non-aqueous electrolyte secondary battery using the same |
US20140099539A1 (en) * | 2012-10-05 | 2014-04-10 | Semiconductor Energy Laboratory Co., Ltd. | Negative electrode for lithium-ion secondary battery, manufacturing method thereof, and lithium-ion secondary battery |
US11322745B2 (en) * | 2014-10-15 | 2022-05-03 | Semiconductor Energy Laboratory Co., Ltd. | Electrode, power storage device, electronic device, and manufacturing method of electrode |
JP2016139521A (en) * | 2015-01-27 | 2016-08-04 | 日産自動車株式会社 | Nonaqueous electrolyte secondary battery |
US11094933B2 (en) * | 2016-07-18 | 2021-08-17 | University Of Kentucky Research Foundation | Polysiloxane binders |
US11682766B2 (en) * | 2017-01-27 | 2023-06-20 | Nec Corporation | Silicone ball containing electrode and lithium ion battery including the same |
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